The synthesis and content of tropomyosins and other cytoskeletal proteins in various human tumor cell lines and tissues will be investigated in order to determine whether synthesis of these proteins is suppressed in human neoplasms as it is in NIH/3T3 cells transformed by oncogenic viruses. Tropomyosins synthesized by various tissue types will be identified by 2-dimensional polyacrylamide gel electrophoresis on the basis of molecular weight, isoelectric point, cytoskeletal localization, absence of tryptophan and immunological reactivity. Expression of tropomyosins in tumor cells of these types will then be evaluated. Synthesis of other cytoskeletal proteins will be evaluated in the same preparations. The following systems will be studied: lymphoid cells, myeloid cells, colon carcinoma, bladder carcinoma, and mammary carcinoma.